If rodent embryos can develop on a spacecraft, there's no reason human ones can't as well.

Chinese scientists have announced a breakthrough in extraterrestrial reproduction: Mouse embryos have successfully been grown on the spacecraft Shijian 10. It’s the first time scientists have successfully nurtured mammalian embryos in space, and it may signify that humans can not only live among the stars but propagate among them as well.

On paper, the goal of the experiment, led by Duan Ennui of the Chinese Academy of Sciences in Beijing, was to investigate the effect space radiation and zero gravity on developing embryos. But Ennui clarified his longer-term vision in an interview with the Communist Party-sanctioned People’s Daily, saying, “We hope [the experiment] will provide scientific support for future human reproductive activities in space.”

Shijian 10, a crewless space lab that launched in early April, carried a microwave-sized chamber containing 6,000 fertilized mouse embryos at the two-cell stage. When the embryos were returned from their 12-day sojourn into space via landing module on Monday, the scientists were thrilled to find that the two-cell balls had developed into blastocysts, much complex entities made up of multiple types of differentiated cells. High-resolution photographs of the developing embryos, snapped every four hours, showed that they developed in line with the stages and timing of normal Earth-bound embryos.

The team’s success is unprecedented, but their dreams of spawning mammalian space babies certainly isn’t.

In 1979, the Soviet Union launched five female and two male mice to space for a two-day, zero-gravity orgy to see whether mammalian space sex could lead to space babies. But the mice didn’t even try. It’s suspected that the weightlessness numbed their libidos.

Mouse embryos at the two-cell stage (left) developed into complex blastocysts (right) during the 12-day trip to space.

And right now, NASA’s running a study called “Space Pup” to test how well freeze-dried mouse sperm holds up to bombardment with cosmic rays and zero-gravity conditions on the ISS.

We’ve hatched fish eggs and fertilized frog eggs in space, but mammalian embryos have, until now, resisted interstellar development. Still, there’s no evidence showing whether they could survive past the blastocyst stage, let alone be delivered — and survive infancy — in space. There’s still a long way to go before we’ll be populating our own space colonies. But we’re definitely more motivated to try.